The present invention relates to line printer registration means and more particularly to a novel registration means employing a gated oscillator whose operation is accurately triggered by light sensing means.
Line printers, especially of the dot matrix type, as disclosed, for example, in U.S. Pat. No. 3,703,949, print vertically aligned dot patterns which are spaced at the desired predetermined intervals along a line of print, the appropriate positioning thereof being obtained by an elongated opaque registration strip arranged therealong and adapted to be positioned between a light sensitive device and a light source in order to develop a "video" pulse as the carriage is moved past each transparent registration slit. The output pulses developed by the phototransistor are ultimately utilized to enable the print head solenoids.
In applications wherein it is desired to provide "normal" spacing between the dot patterns forming each character and to provide "compressed" spacing so as to be able to selectively print, for example, 80 or 132 characters per line of print in the same printer, it is necessary to provide a second registration strip and a second cooperating set of lamp and phototransistor elements. Obviously, in applications wherein it is desired to provide further dot pattern concentrations of even higher densities, additional registration strips and cooperating LEDs and phototransistors must be provided, as well as requiring means for switching between and among the various registration strips, light sources and LEDs.